The invention discloses a synchronous detection controller and control method for grid connection of a micro-grid. Each phase of a three-phase circuit comprises a conditioning circuit module, a first-order anti-aliasing filter difference operation module, a first-order low-pass filter, a detector, a comparator and a D trigger. The synchronous detection controller further comprises a NOR-logic operation module; the synchronous detection controller is applied to the grid connection control of the micro-grid and a public electric network and can effectively ensure the synchronous grid connection, out-of-sync rate is limited within the acceptable range, a large transient state of the micro-grid is avoided, misoperation of a relaying protection system is avoided, safety and stability of operation of the micro-grid are enhanced, and quality of electric energy of the micro-grid is improved. Meanwhile, detection precision is high, wiring is easy, size is small, weight is light, energy consumption and cost are low, high flexibility is achieved, and the synchronous detection controller and control method for the grid connection of the micro-grid are applicable to the grid connection control of the micro-grid.